package test;
import java.util.Scanner;

public class fib {
	
	public static long fib(int n) {
		if(n<=1) {
			return n;
		}
		return fib(n-1)+fib(n-2);
	}

	public static void main(String[] args) {
		Scanner scanner=new Scanner(System.in);
		int t=scanner.nextInt();
		long result=fib(t);
		System.out.println(result);
		scanner.close();
	}

}
